Solved two robo 1+

I don’t think so. You can get an lcd and run them without the computer attached

 

You can run more than one on a PC, but HOW you do this depends on the Printer and it is not straight-forward. As they come from Robo3D the R1 series does not have an embedded computer (like the Raspberry Pi) so you will need to directly control the printers from the host software you are using (mattercontrol, cura, whatever). Each printer will get a different COM port assigned by Windows so just configure your host software to use the printer you want. If you use two different ones you can point each one to its own printer and that will deal with it.

As @Geof pointed out -- if the printer has a smartcontroller (LCD) attached then you can directly print from an SD card with no computer. Also if you use OctoPrint installed on a Raspberry Pi connected to the printer you can print from that and have no other computer attached.